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  Determination of sleep quality for neurological disordersUSPTO Application #: 20070123758Title: Determination of sleep quality for neurological disorders Abstract: A device determines values for one or more metrics that indicate the quality of a patient's sleep based on sensed physiological parameter values. Sleep efficiency, sleep latency, and time spent in deeper sleep states are example sleep quality metrics for which values may be determined. The sleep quality metric values may be used, for example, to evaluate the effectiveness of a therapy delivered to the patient by a medical device. In some embodiments, determined sleep quality metric values are automatically associated with the therapy parameter sets according to which the medical device delivered the therapy when the physiological parameter values were sensed, and used to evaluate the effectiveness of the various therapy parameter sets. The medical device may deliver the therapy to treat a non-respiratory neurological disorder, such as epilepsy, a movement disorder, or a psychological disorder. The therapy may be, for example, deep brain stimulation (DBS) therapy. (end of abstract) Agent: Shumaker & Sieffert, P. A. - Woodbury, MN, US Inventors: Keith A. Miesel, Kenneth T. Heruth, Jonathan C. Werder, Steve LaPorte, Nina M. Graves USPTO Applicaton #: 20070123758 - Class: 600301000 (USPTO) Related Patent Categories: Surgery, Diagnostic Testing, Via Monitoring A Plurality Of Physiological Data, E.g., Pulse And Blood Pressure The Patent Description & Claims data below is from USPTO Patent Application 20070123758. Brief Patent Description - Full Patent Description - Patent Application Claims
[0001] This application is a continuation-in-part of U.S. application Ser. No. 11/081,811, filed Mar. 16, 2005, which is continuation-in-part of U.S. application Ser. No. 10/826,925, filed Apr. 15, 2004, which claims the benefit of U.S. Provisional Application No. 60/553,783, filed Mar. 16, 2004. This application also claims the benefit of U.S. Provisional Application No. 60/785,678, filed Mar. 24, 2006. The entire content of each of these applications is incorporated herein by reference. TECHNICAL FIELD [0002] The invention relates to medical devices and, more particularly, to medical devices that monitor physiological parameters. BACKGROUND [0003] In some cases, an ailment may affect the quality of a patient's sleep. For example, neurological disorders may cause a patient to have difficulty falling asleep, and may disturb the patient's sleep, e.g., cause the patient to wake. Further, neurological disorders may cause the patient to have difficulty achieving deeper sleep states, such as one or more of the nonrapid eye movement (NREM) sleep states. [0004] Epilepsy is an example of a neurological disorder that may affect sleep quality. In some patients, epileptic seizures may be triggered by sleep or transitions between the sleep states, and may occur more frequently during sleep. Furthermore, the occurrence of seizures may disturb sleep, e.g., wake the patient. Often, epilepsy patients are unaware of the seizures that occur while they sleep, and suffer from the effects of disturbed sleep, such as daytime fatigue and concentration problems, without ever knowing why. [0005] Other neurological disorders that may negatively affect patient sleep quality include movement disorders, such as tremor, Parkinson's disease, multiple sclerosis, or spasticity. The uncontrolled movements associated with such movement disorders may cause a patient to have difficulty falling asleep, disturb the patient's sleep, or cause the patient to have difficulty achieving deeper sleep states. Psychological disorders, such as depression, mania, bipolar disorder, or obsessive-compulsive disorder, may also similar affect the ability of a patient to sleep, or at least experience quality sleep. In the case of depression, a patient may "sleep" for long periods of the day, but the sleep is not restful, e.g., includes excessive disturbances and does not include deeper, more restful sleep states. Further, chronic pain, whether of neurological origin or not, as well as congestive heart failure, gastrointestinal disorders and incontinence, may disturb sleep or otherwise affect sleep quality. [0006] Drugs are often used to treat neurological disorders. In some cases, neurological disorders are treated via an implantable medical device (IMD), such as an implantable stimulator or drug delivery device. The treatments for neurological orders may themselves affect sleep quality. [0007] Further, in some cases, poor sleep quality may increase the symptoms experienced by a patient due to a neurological disorder. For example, poor sleep quality has been linked to increased pain symptoms in chronic pain patients and increased seizure activity in epileptic patients, and may also result in increased movement disorder symptoms in movement disorder patients. Further, poor sleep quality may exacerbate many psychological disorders, such as depression. The link between poor sleep quality and increased symptoms is not limited to ailments that negatively impact sleep quality, such as those listed above. Nonetheless, the condition of a patient with such an ailment may progressively worsen when symptoms disturb sleep quality, which in turn increases the frequency and/or intensity of symptoms. SUMMARY [0008] In general, the invention is directed to techniques for collecting information that relates to the quality of patient sleep via a medical device, such as an implantable medical device (IMD). In particular, values for one or more metrics that indicate the quality of the patient's sleep are determined based on at least one sensed physiological parameter signal. In some embodiments, sleep quality information is presented to a user based on the sleep quality metric values. A clinician, for example, may use the presented sleep quality information to evaluate the effectiveness of therapy delivered to the patient by the medical device, to adjust the therapy delivered by the medical device, or to prescribe a therapy not delivered by the medical device in order to improve the quality of the patient's sleep. [0009] In some embodiments, the medical device may deliver the therapy to treat a non-respiratory neurological disorder, such as epilepsy, a movement disorder, or a psychological disorder. As discussed above, examples of movement disorders are tremor, Parkinson's disease, multiple sclerosis, or spasticity, and examples of psychological disorders are depression, mania, bipolar disorder, or obsessive-compulsive disorder. The medical device may be implanted or external, and may deliver, for example, electrical stimulation, a therapeutic agent, such as a drug, and/or a thermal, e.g., cooling, therapy. In some embodiments, the medical device may deliver deep brain stimulation (DBS) therapy to treat a non-respiratory neurological disorder, or other disorder or symptom, and may by implanted on or recessed into the cranium beneath the scalp. [0010] The medical device that delivers the therapy or a separate monitoring device monitors one or more physiological parameter signals. Example physiological parameters include activity level, posture, heart rate, electrocardiogram (ECG) morphology, electroencephalogram (EEG) morphology, respiration rate, respiratory volume, blood pressure, blood oxygen saturation, partial pressure of oxygen within blood, partial pressure of oxygen within cerebrospinal fluid, muscular activity and tone, core temperature, subcutaneous temperature, arterial blood flow, melatonin level within one or more bodily fluids, brain electrical activity, eye motion, and galvanic skin response. In order to monitor one or more of these parameters, the medical device or monitoring device may include, or be coupled to one or more sensors, each of which generates a signal as a function of one or more of these physiological parameters. [0011] The medical device or monitoring device may determine a value of one or more sleep quality metrics based on the one or more monitored physiological parameters, and/or the variability of one or more of the monitored physiological parameters. In other embodiments, one or both of the medical device or monitoring device records values of the one or more physiological parameters, and provides the physiological parameter values to a programming device, such as a clinician programming device or a patient programming device, or another computing device. In such embodiments, the programming or other computing device determines values of one or more sleep quality metrics based on the physiological parameter values received from the medical device and/or the variability of one or more of the physiological parameters. The medical device or monitoring device may provide the recorded physiological parameter values to the programming or other computing device in real time, or may provide physiological parameter values recorded over a period of time to the programming or other computing device when interrogated. [0012] Sleep efficiency and sleep latency are example sleep quality metrics for which a medical device or programming device may determine values. Sleep efficiency may be measured as the percentage of time while the patient is attempting to sleep that the patient is actually asleep. Sleep latency may be measured as the amount of time between a first time when the patient begins attempting to fall asleep and a second time when the patient falls asleep, and thereby indicates how long a patient requires to fall asleep. [0013] The time when the patient begins attempting to fall asleep may be determined in a variety of ways. For example, the patient may provide an indication that he or she is trying to fall asleep, e.g., via a patient programming device. In other embodiments, the medical device or monitoring may monitor the activity level of the patient, and the time when the patient is attempting to fall asleep may be identified by determining whether the patient has remained inactive for a threshold period of time, and identifying the time at which the patient became inactive. In still other embodiments, the medical device or monitoring device may monitor patient posture, and the medical device or a programming device may identify the time when the patient is recumbent, e.g., lying down, as the time when the patient is attempting to fall asleep. In these embodiments, the medical device or monitoring device may also monitor patient activity, and either the medical device, monitoring device, programming device, or other computing device may confirm that the patient is attempting to sleep based on the patient's activity level. [0014] As another example, the medical device or monitoring device may determine the time at which the patient begins attempting to fall asleep based on the level of melatonin within one or more bodily fluids, such as the patient's blood, cerebrospinal fluid (CSF), or interstitial fluid. The medical device or monitoring device may also determine a melatonin level based on metabolites of melatonin located in the saliva or urine of the patient. Melatonin is a hormone secreted by the pineal gland into the bloodstream and the CSF as a function of exposure of the optic nerve to light, which synchronizes the patient's circadian rhythm. In particular, increased levels of melatonin during evening hours may cause physiological changes in the patient, which, in turn, may cause the patient to attempt to fall asleep. The medical device or monitoring device may, for example, detect an increase in the level of melatonin, and estimate the time that the patient will attempt to fall asleep based on the detection. [0015] The time at which the patient has fallen asleep may be determined based on the activity level of the patient and/or one or more of the other physiological parameters that may be monitored by the medical device as indicated above. For example, a discernable change, e.g., a decrease, in one or more physiological parameters, or the variability of one or more physiological parameters, may indicate that the patient has fallen asleep. A decrease in respiration rate or respiration rate variability, or heart rate or heart rate variability, as examples, may indicate that a patient is asleep. [0016] In some embodiments, a sleep probability metric value may be determined based on a value of a physiological parameter monitored by the medical device. In such embodiments, the sleep probability metric value may be compared to a threshold to identify when the patient has fallen asleep. In some embodiments, a plurality of sleep probability metric values are determined based on a value of each of a plurality of physiological parameters, the sleep probability values are averaged or otherwise combined to provide an overall sleep probability metric value, and the overall sleep probability metric value is compared to a threshold to identify the time that the patient falls asleep. [0017] Thus, in some embodiments, whether a patient is sleeping may be determined based on a statistical combination of two or more physiological parameters. For example, whether a patient is sleeping may be determined based on a statistical combination of at least one of activity level or posture, with at least one of brain electrical activity or EEG morphology, and also with core temperatures. Other combinations of the physiological parameters described herein are contemplated. A sleep probability metric value may be determined for each of the physiological parameters based on a current value of the parameter, e.g., by application of an equation or look-up table to the value. The sleep probability metric values may be combined, e.g., by average or sum, which may be weighted, in order to determine whether the patient is asleep based on the plurality of physiological parameters. [0018] Other sleep quality metrics that may be determined include total time sleeping per day, the amount or percentage of time sleeping during nighttime or daytime hours per day, and the number of apnea and/or arousal events per night. In some embodiments, which sleep state the patient is in, e.g., rapid eye movement (REM), or one of the nonrapid eye movement (NREM) states (S1, S2, S3, S4) may be determined based on physiological parameters monitored by the medical device, such as the EEG signal. The amount of time per day spent in these various sleep states may also be a sleep quality metric. Because they provide the most "refreshing" type of sleep, the amount of time spent in one or both of the S3 and S4 sleep states, in particular, may be determined as a sleep quality metric. In some embodiments, average or median values of one or more sleep quality metrics over greater periods of time, e.g., a week or a month, may be determined as the value of the sleep quality metric. Further, in embodiments in which values for a plurality of the sleep quality metrics are determined, a value for an overall sleep quality metric may be determined based on the values for the plurality of individual sleep quality metrics. [0019] As discussed above, in some embodiments, the medical device delivers a therapy. At any given time, the medical device delivers the therapy according to a current set of therapy parameters. For example, in embodiments in which the medical device delivers electrical stimulation, a therapy parameter set may include a pulse amplitude, a pulse width, a pulse rate, a duty cycle, and an indication of active electrodes. Different therapy parameter sets may be selected, e.g., by the patient via a programming device or a the medical device according to a schedule, and parameters of one or more therapy parameter sets may be adjusted by the patient to create new therapy parameter sets. In other words, over time, the medical device delivers the therapy according to a plurality of therapy parameter sets. [0020] In embodiments in which the medical device determines sleep quality metric values, the medical device may identify the current therapy parameter set that was in use when a value of one or more sleep quality metrics is collected, and may associate that value with the therapy parameter set. For each available therapy parameter set the medical device may store a representative value of each of one or more sleep quality metrics in a memory with an indication of the therapy programs with which that representative value is associated. A representative value of sleep quality metric for a therapy parameter set may be the mean or median of collected sleep quality metric values that have been associated with that therapy parameter set. In other embodiments in which a programming device or other computing device determines sleep quality metric values, the medical device may associate recorded physiological parameter values with the current therapy parameter set in the memory. [0021] Further, in embodiments in which a separate monitoring device records physiological parameter values or determines sleep quality metric values, the monitoring device may mark recorded physiological parameter values or sleep quality metric values with a current time in a memory, and the medical device may store an indication of a current therapy parameter set and time in a memory. A programming device or other computing device may receive indications of the physiological parameter values or sleep quality metrics and associated times from the monitoring device, and indications of the therapy parameter sets and associated times from the medical device, and may associate the physiological parameter values or sleep quality metrics with the therapy parameter set that was delivered by the medical device when the physiological parameter values or sleep quality metrics were collected. Continue reading... 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